A Little Known Paper by Professor Fuat Sezgin on the Meridian Instrument of Ibn al-Haytham

When Fuat Sezgin came to Istanbul in 1943, he became a student of mathematics and engineering, only changing to Oriental Studies after meeting Hellmut Ritter. We will analyze a paper which Fuat Sezgin published in 1986 and which is a witness of his mathematical abilities. The paper includes an edition of a mathematically difficult text by Ibn al-Haytham which Sezgin reconstructed from a unique Arabic manuscript written with very few diacritical marks. In this treatise, Ibn al-Haytham discusses the theoretical and practical aspects of an instrument which he produced for determining the meridian with utmost accuracy.